Cold fluids at cryogenic temperatures (e.g., less than −150° C.) pose special handling problems, principally because the temperature of such fluids may quickly lower the temperature of any valve or coupling through which they flow.
When such a coupling is used to transfer a cryogenic fluid, freeze-up problems may occur if the transfer takes place in a moist or high-humidity environment. Any water within, or immediately outside of, the coupling will quickly freeze, thereby potentially impeding subsequent movement of mechanical parts within the coupling. Moreover, successive transfers from a fluid source with the same pre-chilled coupling half to mating coupling halves communicating with different receptacles at warmer ambient temperatures, have been known to result in freeze-up and leakage because of ice formation at the sealing surfaces.
These problems are present in the area of liquefied natural gas (LNG). In order for LNG to be considered as a viable alternative automotive fuel, it must be easily transferred to the vehicle in which it will be used. In addition, it may be desirable for fuel storage tanks on such vehicles be refilled as quickly as possible. This leads to the prospect of multiple quickly-successive short-duration transfers of LNG, at cryogenic temperatures, between a chilled nozzle and a warm receptacle in a potentially-moist environment.
Additionally, when de-coupling a nozzle and receptacle, there may be gas present between the connection that must be vented as de-coupling occurs. Such remainder gas may be at high pressure, and may cause a forceful de-coupling, which can result in injury to users and equipment.
For example, U.S. Pat. No. 5,429,155 to Brzyski et al, and U.S. Pat. No. 6,945,477 to Lambert et al. fail to adequately address these issues. The design of both products makes them prone to freeze-up during operation and fail to provide positive protection against recoil that may occur during the de-coupling of a nozzle and a receptacle.